lkml.org 
[lkml]   [2009]   [Dec]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v5 4/4] memcg: implement memory thresholds
Date
It allows to register multiple memory and memsw thresholds and gets
notifications when it crosses.

To register a threshold application need:
- create an eventfd;
- open memory.usage_in_bytes or memory.memsw.usage_in_bytes;
- write string like "<event_fd> <memory.usage_in_bytes> <threshold>" to
cgroup.event_control.

Application will be notified through eventfd when memory usage crosses
threshold in any direction.

It's applicable for root and non-root cgroup.

It uses stats to track memory usage, simmilar to soft limits. It checks
if we need to send event to userspace on every 100 page in/out. I guess
it's good compromise between performance and accuracy of thresholds.

Signed-off-by: Kirill A. Shutemov <kirill@shutemov.name>
---
Documentation/cgroups/memory.txt | 19 +++-
mm/memcontrol.c | 312 ++++++++++++++++++++++++++++++++++++++
2 files changed, 330 insertions(+), 1 deletions(-)

diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
index b871f25..195af07 100644
--- a/Documentation/cgroups/memory.txt
+++ b/Documentation/cgroups/memory.txt
@@ -414,7 +414,24 @@ NOTE1: Soft limits take effect over a long period of time, since they involve
NOTE2: It is recommended to set the soft limit always below the hard limit,
otherwise the hard limit will take precedence.

-8. TODO
+8. Memory thresholds
+
+Memory controler implements memory thresholds using cgroups notification
+API (see cgroups.txt). It allows to register multiple memory and memsw
+thresholds and gets notifications when it crosses.
+
+To register a threshold application need:
+ - create an eventfd using eventfd(2);
+ - open memory.usage_in_bytes or memory.memsw.usage_in_bytes;
+ - write string like "<event_fd> <memory.usage_in_bytes> <threshold>" to
+ cgroup.event_control.
+
+Application will be notified through eventfd when memory usage crosses
+threshold in any direction.
+
+It's applicable for root and non-root cgroup.
+
+9. TODO

1. Add support for accounting huge pages (as a separate controller)
2. Make per-cgroup scanner reclaim not-shared pages first
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c36d4f3..5d4bd0b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6,6 +6,10 @@
* Copyright 2007 OpenVZ SWsoft Inc
* Author: Pavel Emelianov <xemul@openvz.org>
*
+ * Memory thresholds
+ * Copyright (C) 2009 Nokia Corporation
+ * Author: Kirill A. Shutemov
+ *
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
@@ -39,6 +43,8 @@
#include <linux/mm_inline.h>
#include <linux/page_cgroup.h>
#include <linux/cpu.h>
+#include <linux/eventfd.h>
+#include <linux/sort.h>
#include "internal.h"

#include <asm/uaccess.h>
@@ -56,6 +62,7 @@ static int really_do_swap_account __initdata = 1; /* for remember boot option*/
#endif

#define SOFTLIMIT_EVENTS_THRESH (1000)
+#define THRESHOLDS_EVENTS_THRESH (100)

/*
* Statistics for memory cgroup.
@@ -72,6 +79,8 @@ enum mem_cgroup_stat_index {
MEM_CGROUP_STAT_SWAPOUT, /* # of pages, swapped out */
MEM_CGROUP_STAT_SOFTLIMIT, /* decrements on each page in/out.
used by soft limit implementation */
+ MEM_CGROUP_STAT_THRESHOLDS, /* decrements on each page in/out.
+ used by threshold implementation */

MEM_CGROUP_STAT_NSTATS,
};
@@ -175,6 +184,23 @@ struct mem_cgroup_tree {

static struct mem_cgroup_tree soft_limit_tree __read_mostly;

+struct mem_cgroup_threshold {
+ struct eventfd_ctx *eventfd;
+ u64 threshold;
+};
+
+struct mem_cgroup_threshold_ary {
+ /* An array index points to threshold just below usage. */
+ atomic_t current_threshold;
+ /* Size of entries[] */
+ unsigned int size;
+ /* Array of thresholds */
+ struct mem_cgroup_threshold entries[0];
+};
+
+static bool mem_cgroup_threshold_check(struct mem_cgroup* mem);
+static void mem_cgroup_threshold(struct mem_cgroup* mem);
+
/*
* The memory controller data structure. The memory controller controls both
* page cache and RSS per cgroup. We would eventually like to provide
@@ -226,6 +252,15 @@ struct mem_cgroup {
/* set when res.limit == memsw.limit */
bool memsw_is_minimum;

+ /* protect arrays of thresholds */
+ struct mutex thresholds_lock;
+
+ /* thresholds for memory usage. RCU-protected */
+ struct mem_cgroup_threshold_ary *thresholds;
+
+ /* thresholds for mem+swap usage. RCU-protected */
+ struct mem_cgroup_threshold_ary *memsw_thresholds;
+
/*
* statistics. This must be placed at the end of memcg.
*/
@@ -518,6 +553,8 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *mem,
__mem_cgroup_stat_add_safe(cpustat,
MEM_CGROUP_STAT_PGPGOUT_COUNT, 1);
__mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_SOFTLIMIT, -1);
+ __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_THRESHOLDS, -1);
+
put_cpu();
}

@@ -1503,6 +1540,8 @@ charged:
if (mem_cgroup_soft_limit_check(mem))
mem_cgroup_update_tree(mem, page);
done:
+ if (mem_cgroup_threshold_check(mem))
+ mem_cgroup_threshold(mem);
return 0;
nomem:
css_put(&mem->css);
@@ -2068,6 +2107,8 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)

if (mem_cgroup_soft_limit_check(mem))
mem_cgroup_update_tree(mem, page);
+ if (mem_cgroup_threshold_check(mem))
+ mem_cgroup_threshold(mem);
/* at swapout, this memcg will be accessed to record to swap */
if (ctype != MEM_CGROUP_CHARGE_TYPE_SWAPOUT)
css_put(&mem->css);
@@ -3064,12 +3105,280 @@ static int mem_cgroup_swappiness_write(struct cgroup *cgrp, struct cftype *cft,
return 0;
}

+static bool mem_cgroup_threshold_check(struct mem_cgroup *mem)
+{
+ bool ret = false;
+ int cpu;
+ s64 val;
+ struct mem_cgroup_stat_cpu *cpustat;
+
+ cpu = get_cpu();
+ cpustat = &mem->stat.cpustat[cpu];
+ val = __mem_cgroup_stat_read_local(cpustat, MEM_CGROUP_STAT_THRESHOLDS);
+ if (unlikely(val < 0)) {
+ __mem_cgroup_stat_set_safe(cpustat, MEM_CGROUP_STAT_THRESHOLDS,
+ THRESHOLDS_EVENTS_THRESH);
+ ret = true;
+ }
+ put_cpu();
+ return ret;
+}
+
+static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap)
+{
+ struct mem_cgroup_threshold_ary *t;
+ u64 usage;
+ int i;
+
+ rcu_read_lock();
+ if (!swap) {
+ t = rcu_dereference(memcg->thresholds);
+ } else {
+ t = rcu_dereference(memcg->memsw_thresholds);
+ }
+
+ if (!t)
+ goto unlock;
+
+ usage = mem_cgroup_usage(memcg, swap);
+
+ /*
+ * current_threshold points to threshold just below usage.
+ * If it's not true, a threshold was crossed after last
+ * call of __mem_cgroup_threshold().
+ */
+ i = atomic_read(&t->current_threshold);
+
+ /*
+ * Iterate backward over array of thresholds starting from
+ * current_threshold and check if a threshold is crossed.
+ * If none of thresholds below usage is crossed, we read
+ * only one element of the array here.
+ */
+ for(; i > 0 && unlikely(t->entries[i].threshold > usage); i--) {
+ eventfd_signal(t->entries[i].eventfd, 1);
+ }
+
+ /* i = current_threshold + 1 */
+ i++;
+
+ /*
+ * Iterate forward over array of thresholds starting from
+ * current_threshold+1 and check if a threshold is crossed.
+ * If none of thresholds above usage is crossed, we read
+ * only one element of the array here.
+ */
+ for(; i < t->size && unlikely(t->entries[i].threshold <= usage); i++) {
+ eventfd_signal(t->entries[i].eventfd, 1);
+ }
+
+ /* Update current_threshold */
+ atomic_set(&t->current_threshold, i - 1);
+unlock:
+ rcu_read_unlock();
+}
+
+static void mem_cgroup_threshold(struct mem_cgroup *memcg)
+{
+ __mem_cgroup_threshold(memcg, false);
+ if (do_swap_account)
+ __mem_cgroup_threshold(memcg, true);
+}
+
+static int compare_thresholds(const void *a, const void *b)
+{
+ const struct mem_cgroup_threshold *_a = a;
+ const struct mem_cgroup_threshold *_b = b;
+
+ return _a->threshold - _b->threshold;
+}
+
+static int mem_cgroup_register_event(struct cgroup *cgrp, struct cftype *cft,
+ struct eventfd_ctx *eventfd, const char *args)
+{
+ struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+ struct mem_cgroup_threshold_ary *thresholds, *thresholds_new;
+ int type = MEMFILE_TYPE(cft->private);
+ u64 threshold, usage;
+ int size;
+ int i, ret;
+
+ ret = res_counter_memparse_write_strategy(args, &threshold);
+ if (ret)
+ return ret;
+
+ mutex_lock(&memcg->thresholds_lock);
+ if (type == _MEM)
+ thresholds = memcg->thresholds;
+ else if (type == _MEMSWAP)
+ thresholds = memcg->memsw_thresholds;
+ else
+ BUG();
+
+ usage = mem_cgroup_usage(memcg, type == _MEMSWAP);
+
+ /* Check if a threshold crossed before adding a new one */
+ if (thresholds)
+ __mem_cgroup_threshold(memcg, type == _MEMSWAP);
+
+ if (thresholds)
+ size = thresholds->size + 1;
+ else
+ size = 1;
+
+ /* Allocate memory for new array of thresholds */
+ thresholds_new = kmalloc(sizeof(*thresholds_new) +
+ size * sizeof(struct mem_cgroup_threshold),
+ GFP_KERNEL);
+ if (!thresholds_new) {
+ ret = -ENOMEM;
+ goto unlock;
+ }
+ thresholds_new->size = size;
+
+ /* Copy thresholds (if any) to new array */
+ if (thresholds)
+ memcpy(thresholds_new->entries, thresholds->entries,
+ thresholds->size *
+ sizeof(struct mem_cgroup_threshold));
+ /* Add new threshold */
+ thresholds_new->entries[size - 1].eventfd = eventfd;
+ thresholds_new->entries[size - 1].threshold = threshold;
+
+ /* Sort thresholds. Registering of new threshold isn't time-critical */
+ sort(thresholds_new->entries, size,
+ sizeof(struct mem_cgroup_threshold),
+ compare_thresholds, NULL);
+
+ /* Find current threshold */
+ atomic_set(&thresholds_new->current_threshold, -1);
+ for(i = 0; i < size; i++) {
+ if (thresholds_new->entries[i].threshold < usage) {
+ /*
+ * thresholds_new->current_threshold will not be used
+ * until rcu_assign_pointer(), so it's safe to increment
+ * it here.
+ */
+ atomic_inc(&thresholds_new->current_threshold);
+ }
+ }
+
+ /*
+ * We need to increment refcnt to be sure that all thresholds
+ * will be unregistered before calling __mem_cgroup_free()
+ */
+ mem_cgroup_get(memcg);
+
+ if (type == _MEM)
+ rcu_assign_pointer(memcg->thresholds, thresholds_new);
+ else
+ rcu_assign_pointer(memcg->memsw_thresholds, thresholds_new);
+
+ /* To be sure that nobody uses thresholds before freeing it */
+ synchronize_rcu();
+
+ kfree(thresholds);
+unlock:
+ mutex_unlock(&memcg->thresholds_lock);
+
+ return ret;
+}
+
+static int mem_cgroup_unregister_event(struct cgroup *cgrp, struct cftype *cft,
+ struct eventfd_ctx *eventfd)
+{
+ struct mem_cgroup *memcg = mem_cgroup_from_cont(cgrp);
+ struct mem_cgroup_threshold_ary *thresholds, *thresholds_new;
+ int type = MEMFILE_TYPE(cft->private);
+ u64 usage;
+ int size = 0;
+ int i, j, ret;
+
+ mutex_lock(&memcg->thresholds_lock);
+ if (type == _MEM)
+ thresholds = memcg->thresholds;
+ else if (type == _MEMSWAP)
+ thresholds = memcg->memsw_thresholds;
+ else
+ BUG();
+
+ /*
+ * Something went wrong if we trying to unregister a threshold
+ * if we don't have thresholds
+ */
+ BUG_ON(!thresholds);
+
+ usage = mem_cgroup_usage(memcg, type == _MEMSWAP);
+
+ /* Check if a threshold crossed before removing */
+ __mem_cgroup_threshold(memcg, type == _MEMSWAP);
+
+ /* Calculate new number of threshold */
+ for(i = 0; i < thresholds->size; i++) {
+ if (thresholds->entries[i].eventfd != eventfd)
+ size++;
+ }
+
+ /* Set thresholds array to NULL if we don't have thresholds */
+ if (!size) {
+ thresholds_new = NULL;
+ goto assign;
+ }
+
+ /* Allocate memory for new array of thresholds */
+ thresholds_new = kmalloc(sizeof(*thresholds_new) +
+ size * sizeof(struct mem_cgroup_threshold),
+ GFP_KERNEL);
+ if (!thresholds_new) {
+ ret = -ENOMEM;
+ goto unlock;
+ }
+ thresholds_new->size = size;
+
+ /* Copy thresholds and find current threshold */
+ atomic_set(&thresholds_new->current_threshold, -1);
+ for(i = 0, j = 0; i < thresholds->size; i++) {
+ if (thresholds->entries[i].eventfd == eventfd)
+ continue;
+
+ thresholds_new->entries[j] = thresholds->entries[i];
+ if (thresholds_new->entries[j].threshold < usage) {
+ /*
+ * thresholds_new->current_threshold will not be used
+ * until rcu_assign_pointer(), so it's safe to increment
+ * it here.
+ */
+ atomic_inc(&thresholds_new->current_threshold);
+ }
+ j++;
+ }
+
+assign:
+ if (type == _MEM)
+ rcu_assign_pointer(memcg->thresholds, thresholds_new);
+ else
+ rcu_assign_pointer(memcg->memsw_thresholds, thresholds_new);
+
+ /* To be sure that nobody uses thresholds before freeing it */
+ synchronize_rcu();
+
+ for(i = 0; i < thresholds->size - size; i++)
+ mem_cgroup_put(memcg);
+
+ kfree(thresholds);
+unlock:
+ mutex_unlock(&memcg->thresholds_lock);
+
+ return ret;
+}

static struct cftype mem_cgroup_files[] = {
{
.name = "usage_in_bytes",
.private = MEMFILE_PRIVATE(_MEM, RES_USAGE),
.read_u64 = mem_cgroup_read,
+ .register_event = mem_cgroup_register_event,
+ .unregister_event = mem_cgroup_unregister_event,
},
{
.name = "max_usage_in_bytes",
@@ -3121,6 +3430,8 @@ static struct cftype memsw_cgroup_files[] = {
.name = "memsw.usage_in_bytes",
.private = MEMFILE_PRIVATE(_MEMSWAP, RES_USAGE),
.read_u64 = mem_cgroup_read,
+ .register_event = mem_cgroup_register_event,
+ .unregister_event = mem_cgroup_unregister_event,
},
{
.name = "memsw.max_usage_in_bytes",
@@ -3360,6 +3671,7 @@ mem_cgroup_create(struct cgroup_subsys *ss, struct cgroup *cont)
if (parent)
mem->swappiness = get_swappiness(parent);
atomic_set(&mem->refcnt, 1);
+ mutex_init(&mem->thresholds_lock);
return &mem->css;
free_out:
__mem_cgroup_free(mem);
--
1.6.5.7


\
 
 \ /
  Last update: 2009-12-30 17:01    [W:0.086 / U:2.740 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site